1. The Field of the Invention
This invention is in the field of apparatus and methods for dilating bodily tissue in order to provide surgical access to a desired area of the body, such as for providing surgical access to the spine.
2. The Relevant Technology
Dilation systems are employed to move the skin, muscle, and other bodily tissues away from a surgical site in order to provide a surgeon access to bone or other bodily tissue where surgery is required. In a spinal surgery, for example, it is often desired to separate the skin and other tissue away from a particular desired surgical site prior to surgery. In order to perform this function, the skin and other tissue may be pulled away from the insertion site and a retractor placed in the insertion site to retain the skin and other tissue away from the surgical site during the surgical procedure.
One example of a dilation system that is employed during such a surgery is a dilation system having a plurality of tubular members that can be concentrically disposed. Each tubular member has a uniformly smooth interior surface and exterior surface. Initially, a guide wire is inserted within a small incision formed at the surgical site. Next, a smallest first tubular member is feed over the guide wire so that a distal end of the first tubular member is advanced into the surgical site. As the distal end advances into the incision, the tissue surrounding the first tubular member is radially outwardly retracted or dilated.
Once the first tubular member is inserted to a desired depth, a slightly larger second tubular member is pushed over the second tubular member and into the tissue so as to further dilate the tissue. This process is repeated for additionally larger tubular members until the tissue at the surgical site is retracted to a desired extent to facilitate the surgical procedure.
Although conventional dilation systems function to retract the tissue, they have a number of shortcomings. For example, it is often desirable to have each subsequent tubular member penetrate to the same depth in the tissue as the first tubular member. In conventional systems, however, it is difficult to know the exact depth that each tubular member is inserted. Furthermore, conventional tubular member are simply pushed into the tissue. Because of applied friction forces produced by the tissue, it is often difficult to advance each tubular member to a desired depth without over penetrating. That is, as static friction forces are initially overcome, the pushing force applied to a tubular member can cause the tubular member to advance too far into the tissue.